I had someone ask me this question recently, and here’s the answer:
When I talk to people about building their brand and showcasing their talents, I suggest blogging as the best way to display their skills. However after they ask about finding topics, the next question is invariably about how often to blog. My answer? As often as is comfortable for you.
What I suggest to most people is that they set aside time for writing and then use Word, Notepad, or any editor to draft posts. Write ten posts on whatever topics you like, and see how long it takes to complete them. Get feedback from friends, re-read them a day or so later, and count them finished when you’d be comfortable to publish them. Then schedule the ten posts based on your pace of writing. Perhaps 10 posts takes you a month, maybe it takes you ten months, but whatever time required is your pace. It may change over time, but blog at whatever rate fits in your life.